The invention is based on a valve for gaseous and/or liquid flow media, in particular a pressure control valve for an exhaust recirculation valve in internal combustion engines.
In a known pressure control valve for controlling an exhaust recirculation valve in an internal combustion engine, the delivery opening communicates with the vacuum chamber of the exhaust recirculation valve, with which the quantity of exhaust gas delivered to the fuel-air mixture in the intake tube is regulated. For controlling the vacuum in the valve interior in accordance with the operating status of the motor vehicle engine, the valve opening of the pressure control valve communicates with a source of vacuum via a vacuum line, and the valve closing member is actuated counter to the force of a valve opening spring by a differential pressure transducer disposed in the fuel supply line. If a larger quantity of fuel is injected by the fuel injection pump, for instance, during an acceleration of the motor vehicle, then the pressure drop in the differential pressure transducer increases as a result. The differential pressure transducer accordingly actuates the valve closing member in the closing direction, causing the vacuum from the vacuum source to be less effective in the valve interior. The valve interior is simultaneously relieved via a throttle. As the vacuum in the valve interior lessens i.e. as the actual pressure increases approaching atmospheric pressure, the exhaust recirculation valve is closed to an increasing extent by a closing spring, so that there is a lower rate of exhaust feedback to the intake tube. In the closed position of the pressure control valve, the valve closing member rests on the valve seat surrounding the valve opening and seals off the valve opening completely.
As the fuel injection quantity is reduced, a greater quantity of exhaust gas has to be supplied. The thereby lessening vacuum in the differential pressure transducer thus causes the pressure control valve to open once again. However, the pressure control valve does have a certain hysteresis in opening; that is, as the opening process is initiated, a certain opening force must first be brought to bear before the valve closing member will rise from the valve seat. This hysteresis in opening is a critical disturbing factor in regulating the delivery of the metered exhaust gas rate.